Exam 200-310 topic 2 question 96 discussion

Actual exam question from Cisco's 200-310

Question #: 96
Topic #: 2

On a Cisco router, which of the following commands relies on ICMP TEMs to map the path that a packet takes as it passes through a network?

A. ping
B. traceroute
C. arp
D. netconf

Show Suggested Answer

Suggested Answer: B 🗳️
Section: Design Methodologies Explanation

On a Cisco router, the traceroute command relies on Internet Control Message Protocol (ICMP) Time Exceeded Messages (TEMs) to map the path that a packet takes as it passes through a network. The traceroute command works by sending a sequence of messages, usually User Datagram Protocol (UDP) packets, to a destination address. The Time-to-Live (TTL) value in the IP header of each series of packets is incremented as the traceroute command discovers the IP address of each router in the path to the destination address. The first series of packets, which have a TTL value of one, make it to the first hop router, where their TTL value is decremented by one as part of the forwarding process. Because the new TTL value of each of these packets will be zero, the first hop router will discard the packets and send an ICMP TEM to the source of each discarded packet. The traceroute command will record the IP address of the source of the ICMP TEM and will then send a new series of messages with a higher TTL. The next series of messages is sent with a TTL value of two and arrives at the second hop before generating ICMP TEMs and thus identifying the second hop. This process continues until the destination is reached and every hop in the path to the destination is identified. In this manner, the traceroute command can be used to manually build a topology map of an existing network? however, more effective mechanisms, such as Link Layer Discovery Protocol (LLDP) or Cisco Discovery Protocol (CDP), are typically used instead when available.
The ping command does not rely on TEMs to map the path that a packet takes as it passes through a network. The ping command sends ICMP Echo Request messages to a destination address and waits for the corresponding ICMP Echo Reply messages to be sent back. Most implementations of ping report additional statistics, such as the number of packets dropped and the length of time that lapsed between a request and the reply. Although the ping command can be used to determine connectivity to a destination, it cannot be used to trace the route taken by a packet as it moves toward its destination.
The arp command does not rely on TEMs to map the path that a packet takes as it passes through a network. On a Cisco router, the arp command can be used in global configuration mode to create a static entry in the local Address Resolution Protocol (ARP) cache. For example, the arp 198.51.1.11
000c.0101.0101 arp a command creates a manual entry in the ARP table to map the IP address 198.51.1.11 to an Ethernet Media Access Control (MAC) address of 000c.0101.0101.
The net-conf command does not rely on TEMs to map the path that a packet takes as it passes through a network. The net-conf command can be used to configure Network Configuration Protocol (NETCONF) parameters on a Cisco device. NETCONF is an Internet Engineering Task Force (IETF) standard that uses
Extensible Markup Language (XML) messages to manage the configuration of network devices. With NETCONF, a client can lock the configuration data on a device and then retrieve the entire configuration in a standardized, parsable format without fear of the configuration changing during the session. The client can then modify the configuration as needed and send the updated configuration data to the device for implementation before releasing the session lock.
Reference:
Cisco: Understanding the Ping and Traceroute Commands

by [deleted] at April 3, 2025, 1:53 a.m.

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